Twelve-year-old Julia has very firm views. "I'm an atheist. I believe in the big bang and stuff. I don't believe in God. I don't sing hymns and I don't pray. I'm the only non-Christian in my class at school and sometimes that can cause a problem. Some people think I'm a bit weird."

Then, as the rain started to pour, she dashed into a big, baggy army tent and joined the rest of her new friends for the first session of the day: philosophy.

This is Camp Quest, billed as Britain's first summer camp for young atheists. It's only day three of the five-day programme taking place in a soggy field in Somerset, but already the event has attracted criticism from parts of the media (the Daily Mail dubbed it "Camp Faithless") and, unsurprisingly, scepticism from the Church of England.

The idea behind the camp is to give a "godless" alternative to traditional religious summer camps. In the morning the participants discuss philosophical ideas and learn about subjects such as astronomy. Then in the afternoons they take part in more traditional camp activities. They swim, they run, they climb, they row. In the evening – if the rain relents – they sit round the campfire and toast marshmallows.

So Julia said she really enjoyed the Charles Darwin talk, but also loved scrambling over a great big wall. "But the best thing is that they tell you it doesn't matter what you believe – just believe it and stick with it."

The first Camp Quest took place in the US in 1996. Supported with a modest grant from the Richard Dawkins Foundation, Camp Quest UK has been founded to give the children of "atheists, agnostics, humanists, freethinkers and all those who embrace a naturalistic rather than supernatural world view" a summer camp experience not tinged with religion.

Twenty-three youngsters aged from six or seven (there was some dispute today about the age of the youngest child; the organisers thought he was seven, little Leroy insisted he was six) are attending the Somerset mud and think-fest.

First session this morning was philosophy. The starting point was Hans Christian Andersen's story of the emperor's new clothes. Dianna Moylan, a 67-year-old former teacher, barn dance musician and "successful atheist – not a failed Christian", told the tale, then organised the children into three groups. They were asked to discuss the story and come up with philosophical questions about it.

First they decided what a philosophical question was. One of the boys, Matthew, went with: "Why are we here?" It was taken as philosophy rather than a complaint.

They went on to discuss why the cheating tailors, who take the emperor's money and convince him that they have made an invisible outfit for him, had been intent on tricking him. Did they need the money because they were poor? And if they were poor could they have been justified?

From the depths of a big blue cagoule, Julius, the youngest in this group, was impressed with the little boy who came forward and pointed out that the emperor was naked as he paraded through the streets.

Moylan asked Julius if he thought that he could be right even if bigger people told him he was wrong. "I can be right," he replied.

Julia chipped in. "Why do older people not listen to the younger generation? They don't ask younger people stuff." She sounded a bit huffy but she probably had a point.

To cut a long discussion short, they came up with two questions to take back to the bigger group. Firstly, if everyone believed something – such as the idea that the emperor really did have an invisible outfit on – was it as good as fact? And secondly, was it ever OK to lie?

Moylan was pleased. "They are being taught to be thinkers, not atheists. Think, make decisions for yourself."

A quick break and then Jens Christensen, who is originally from Denmark but is the proud founder of the local atheist society in Southampton, where he is studying engineering, blew a whistle and called the campers in for astronomy.

He started to explain how we are all connected to the planets. How are we made and where do we come from? he asked.

Leroy, the boy who insists he is six (and this is not the sort of place where you doubt children), shouted out: "Stardust".

Christensen told him that he might be right in a way. "We are all part of the universe and the universe is part of us," said Christensen. Then he was asked how big the universe was and it all started getting very complicated.

Which pleases Samantha Stein, the director of Camp Quest UK. "We try to teach them how to think and not what to think. We're encouraging them to leave camp with 101 questions for their parents and teachers. And that's got to be a good thing."